Simultaneous and divergent evolution of resistance to cephalosporin/β-lactamase inhibitor combinations and imipenem/relebactam following ceftazidime/avibactam treatment of MDR Pseudomonas aeruginosa infections.

We demonstrated how P. aeruginosa may simultaneously develop resistance and compromise the activity of new β-lactam/β-lactamase inhibitor combinations when exposed to ceftazidime/avibactam through selection of mutations leading to PDC modification and up-regulation of MexAB-OprM-mediated efflux.